165 lines
6.9 KiB
Diff
165 lines
6.9 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Sean Christopherson <seanjc@google.com>
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Date: Wed, 27 Sep 2023 17:19:52 -0700
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Subject: [PATCH] x86/fpu: Allow caller to constrain xfeatures when copying to
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uabi buffer
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Plumb an xfeatures mask into __copy_xstate_to_uabi_buf() so that KVM can
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constrain which xfeatures are saved into the userspace buffer without
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having to modify the user_xfeatures field in KVM's guest_fpu state.
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KVM's ABI for KVM_GET_XSAVE{2} is that features that are not exposed to
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guest must not show up in the effective xstate_bv field of the buffer.
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Saving only the guest-supported xfeatures allows userspace to load the
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saved state on a different host with a fewer xfeatures, so long as the
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target host supports the xfeatures that are exposed to the guest.
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KVM currently sets user_xfeatures directly to restrict KVM_GET_XSAVE{2} to
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the set of guest-supported xfeatures, but doing so broke KVM's historical
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ABI for KVM_SET_XSAVE, which allows userspace to load any xfeatures that
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are supported by the *host*.
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Cc: stable@vger.kernel.org
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Signed-off-by: Sean Christopherson <seanjc@google.com>
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Message-Id: <20230928001956.924301-2-seanjc@google.com>
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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(cherry picked from commit 18164f66e6c59fda15c198b371fa008431efdb22)
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Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
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---
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arch/x86/include/asm/fpu/api.h | 3 ++-
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arch/x86/kernel/fpu/core.c | 5 +++--
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arch/x86/kernel/fpu/xstate.c | 7 +++++--
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arch/x86/kernel/fpu/xstate.h | 3 ++-
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arch/x86/kvm/x86.c | 21 +++++++++------------
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5 files changed, 21 insertions(+), 18 deletions(-)
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diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h
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index b475d9a582b8..e829fa4c6788 100644
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--- a/arch/x86/include/asm/fpu/api.h
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+++ b/arch/x86/include/asm/fpu/api.h
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@@ -148,7 +148,8 @@ static inline void fpu_update_guest_xfd(struct fpu_guest *guest_fpu, u64 xfd) {
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static inline void fpu_sync_guest_vmexit_xfd_state(void) { }
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#endif
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-extern void fpu_copy_guest_fpstate_to_uabi(struct fpu_guest *gfpu, void *buf, unsigned int size, u32 pkru);
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+extern void fpu_copy_guest_fpstate_to_uabi(struct fpu_guest *gfpu, void *buf,
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+ unsigned int size, u64 xfeatures, u32 pkru);
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extern int fpu_copy_uabi_to_guest_fpstate(struct fpu_guest *gfpu, const void *buf, u64 xcr0, u32 *vpkru);
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static inline void fpstate_set_confidential(struct fpu_guest *gfpu)
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diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
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index 98e507cc7d34..b582325b9c37 100644
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--- a/arch/x86/kernel/fpu/core.c
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+++ b/arch/x86/kernel/fpu/core.c
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@@ -369,14 +369,15 @@ int fpu_swap_kvm_fpstate(struct fpu_guest *guest_fpu, bool enter_guest)
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EXPORT_SYMBOL_GPL(fpu_swap_kvm_fpstate);
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void fpu_copy_guest_fpstate_to_uabi(struct fpu_guest *gfpu, void *buf,
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- unsigned int size, u32 pkru)
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+ unsigned int size, u64 xfeatures, u32 pkru)
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{
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struct fpstate *kstate = gfpu->fpstate;
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union fpregs_state *ustate = buf;
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struct membuf mb = { .p = buf, .left = size };
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if (cpu_feature_enabled(X86_FEATURE_XSAVE)) {
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- __copy_xstate_to_uabi_buf(mb, kstate, pkru, XSTATE_COPY_XSAVE);
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+ __copy_xstate_to_uabi_buf(mb, kstate, xfeatures, pkru,
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+ XSTATE_COPY_XSAVE);
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} else {
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memcpy(&ustate->fxsave, &kstate->regs.fxsave,
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sizeof(ustate->fxsave));
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diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
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index 1afbc4866b10..463ec0cd0dab 100644
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--- a/arch/x86/kernel/fpu/xstate.c
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+++ b/arch/x86/kernel/fpu/xstate.c
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@@ -1053,6 +1053,7 @@ static void copy_feature(bool from_xstate, struct membuf *to, void *xstate,
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* __copy_xstate_to_uabi_buf - Copy kernel saved xstate to a UABI buffer
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* @to: membuf descriptor
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* @fpstate: The fpstate buffer from which to copy
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+ * @xfeatures: The mask of xfeatures to save (XSAVE mode only)
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* @pkru_val: The PKRU value to store in the PKRU component
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* @copy_mode: The requested copy mode
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*
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@@ -1063,7 +1064,8 @@ static void copy_feature(bool from_xstate, struct membuf *to, void *xstate,
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* It supports partial copy but @to.pos always starts from zero.
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*/
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void __copy_xstate_to_uabi_buf(struct membuf to, struct fpstate *fpstate,
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- u32 pkru_val, enum xstate_copy_mode copy_mode)
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+ u64 xfeatures, u32 pkru_val,
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+ enum xstate_copy_mode copy_mode)
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{
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const unsigned int off_mxcsr = offsetof(struct fxregs_state, mxcsr);
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struct xregs_state *xinit = &init_fpstate.regs.xsave;
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@@ -1087,7 +1089,7 @@ void __copy_xstate_to_uabi_buf(struct membuf to, struct fpstate *fpstate,
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break;
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case XSTATE_COPY_XSAVE:
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- header.xfeatures &= fpstate->user_xfeatures;
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+ header.xfeatures &= fpstate->user_xfeatures & xfeatures;
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break;
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}
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@@ -1189,6 +1191,7 @@ void copy_xstate_to_uabi_buf(struct membuf to, struct task_struct *tsk,
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enum xstate_copy_mode copy_mode)
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{
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__copy_xstate_to_uabi_buf(to, tsk->thread.fpu.fpstate,
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+ tsk->thread.fpu.fpstate->user_xfeatures,
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tsk->thread.pkru, copy_mode);
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}
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diff --git a/arch/x86/kernel/fpu/xstate.h b/arch/x86/kernel/fpu/xstate.h
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index a4ecb04d8d64..3518fb26d06b 100644
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--- a/arch/x86/kernel/fpu/xstate.h
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+++ b/arch/x86/kernel/fpu/xstate.h
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@@ -43,7 +43,8 @@ enum xstate_copy_mode {
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struct membuf;
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extern void __copy_xstate_to_uabi_buf(struct membuf to, struct fpstate *fpstate,
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- u32 pkru_val, enum xstate_copy_mode copy_mode);
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+ u64 xfeatures, u32 pkru_val,
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+ enum xstate_copy_mode copy_mode);
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extern void copy_xstate_to_uabi_buf(struct membuf to, struct task_struct *tsk,
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enum xstate_copy_mode mode);
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extern int copy_uabi_from_kernel_to_xstate(struct fpstate *fpstate, const void *kbuf, u32 *pkru);
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diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
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index 6690a3722007..394d3a8b4682 100644
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--- a/arch/x86/kvm/x86.c
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+++ b/arch/x86/kvm/x86.c
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@@ -5385,26 +5385,23 @@ static int kvm_vcpu_ioctl_x86_set_debugregs(struct kvm_vcpu *vcpu,
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return 0;
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}
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-static void kvm_vcpu_ioctl_x86_get_xsave(struct kvm_vcpu *vcpu,
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- struct kvm_xsave *guest_xsave)
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+
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+static void kvm_vcpu_ioctl_x86_get_xsave2(struct kvm_vcpu *vcpu,
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+ u8 *state, unsigned int size)
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{
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if (fpstate_is_confidential(&vcpu->arch.guest_fpu))
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return;
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- fpu_copy_guest_fpstate_to_uabi(&vcpu->arch.guest_fpu,
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- guest_xsave->region,
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- sizeof(guest_xsave->region),
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+ fpu_copy_guest_fpstate_to_uabi(&vcpu->arch.guest_fpu, state, size,
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+ vcpu->arch.guest_fpu.fpstate->user_xfeatures,
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vcpu->arch.pkru);
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}
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-static void kvm_vcpu_ioctl_x86_get_xsave2(struct kvm_vcpu *vcpu,
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- u8 *state, unsigned int size)
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+static void kvm_vcpu_ioctl_x86_get_xsave(struct kvm_vcpu *vcpu,
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+ struct kvm_xsave *guest_xsave)
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{
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- if (fpstate_is_confidential(&vcpu->arch.guest_fpu))
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- return;
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-
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- fpu_copy_guest_fpstate_to_uabi(&vcpu->arch.guest_fpu,
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- state, size, vcpu->arch.pkru);
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+ return kvm_vcpu_ioctl_x86_get_xsave2(vcpu, (void *)guest_xsave->region,
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+ sizeof(guest_xsave->region));
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}
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static int kvm_vcpu_ioctl_x86_set_xsave(struct kvm_vcpu *vcpu,
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