[patch 16/31] x86/fpu: Replace KVMs homebrewn FPU copy to user

Thomas Gleixner
2021-10-12T00:06:47Z

Similar to the copy from user function the FPU core has this already
implemented with all bells and whistels.

Get rid of the duplicated code and use the core functionality.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/include/asm/fpu/api.h | 2 -
arch/x86/kernel/fpu/core.c | 16 +++++++++++
arch/x86/kvm/x86.c | 56 ++---------------------------------------
3 files changed, 20 insertions(+), 54 deletions(-)

--- a/arch/x86/include/asm/fpu/api.h
+++ b/arch/x86/include/asm/fpu/api.h
@@ -116,7 +116,7 @@ extern void fpu_init_fpstate_user(struct
/* KVM specific functions */
extern void fpu_swap_kvm_fpu(struct fpu *save, struct fpu *rstor, u64 restore_mask);

-struct kvm_vcpu;
extern int fpu_copy_kvm_uabi_to_vcpu(struct fpu *fpu, const void *buf, u64 xcr0, u32 *pkru);
+extern void fpu_copy_vcpu_to_kvm_uabi(struct fpu *fpu, void *buf, unsigned int size, u32 pkru);

#endif /* _ASM_X86_FPU_API_H */
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -175,6 +175,22 @@ void fpu_swap_kvm_fpu(struct fpu *save,
}
EXPORT_SYMBOL_GPL(fpu_swap_kvm_fpu);

+void fpu_copy_vcpu_to_kvm_uabi(struct fpu *fpu, void *buf,
+ unsigned int size, u32 pkru)
+{
+ union fpregs_state *kstate = &fpu->state;
+ union fpregs_state *ustate = buf;
+ struct membuf mb = { .p = buf, .left = size };
+
+ if (cpu_feature_enabled(X86_FEATURE_XSAVE)) {
+ __copy_xstate_to_uabi_buf(mb, &kstate->xsave, pkru,
+ XSTATE_COPY_XSAVE);
+ } else {
+ memcpy(&ustate->fxsave, &kstate->fxsave, sizeof(ustate->fxsave));
+ }
+}
+EXPORT_SYMBOL_GPL(fpu_copy_vcpu_to_kvm_uabi);
+
int fpu_copy_kvm_uabi_to_vcpu(struct fpu *fpu, const void *buf, u64 xcr0,
u32 *vpkru)
{
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4695,65 +4695,15 @@ static int kvm_vcpu_ioctl_x86_set_debugr
return 0;
}

-static void fill_xsave(u8 *dest, struct kvm_vcpu *vcpu)
-{
- struct xregs_state *xsave = &vcpu->arch.guest_fpu->state.xsave;
- u64 xstate_bv = xsave->header.xfeatures;
- u64 valid;
-
- /*
- * Copy legacy XSAVE area, to avoid complications with CPUID
- * leaves 0 and 1 in the loop below.
- */
- memcpy(dest, xsave, XSAVE_HDR_OFFSET);
-
- /* Set XSTATE_BV */
- xstate_bv &= vcpu->arch.guest_supported_xcr0 | XFEATURE_MASK_FPSSE;
- *(u64 *)(dest + XSAVE_HDR_OFFSET) = xstate_bv;
-
- /*
- * Copy each region from the possibly compacted offset to the
- * non-compacted offset.
- */
- valid = xstate_bv & ~XFEATURE_MASK_FPSSE;
- while (valid) {
- u32 size, offset, ecx, edx;
- u64 xfeature_mask = valid & -valid;
- int xfeature_nr = fls64(xfeature_mask) - 1;
- void *src;
-
- cpuid_count(XSTATE_CPUID, xfeature_nr,
- &size, &offset, &ecx, &edx);
-
- if (xfeature_nr == XFEATURE_PKRU) {
- memcpy(dest + offset, &vcpu->arch.pkru,
- sizeof(vcpu->arch.pkru));
- } else {
- src = get_xsave_addr(xsave, xfeature_nr);
- if (src)
- memcpy(dest + offset, src, size);
- }
-
- valid -= xfeature_mask;
- }
-}
-
static void kvm_vcpu_ioctl_x86_get_xsave(struct kvm_vcpu *vcpu,
struct kvm_xsave *guest_xsave)
{
if (!vcpu->arch.guest_fpu)
return;

- if (boot_cpu_has(X86_FEATURE_XSAVE)) {
- memset(guest_xsave, 0, sizeof(struct kvm_xsave));
- fill_xsave((u8 *) guest_xsave->region, vcpu);
- } else {
- memcpy(guest_xsave->region,
- &vcpu->arch.guest_fpu->state.fxsave,
- sizeof(struct fxregs_state));
- *(u64 *)&guest_xsave->region[XSAVE_HDR_OFFSET / sizeof(u32)] =
- XFEATURE_MASK_FPSSE;
- }
+ fpu_copy_vcpu_to_kvm_uabi(vcpu->arch.guest_fpu, guest_xsave->region,
+ sizeof(guest_xsave->region),
+ vcpu->arch.pkru);
}

static int kvm_vcpu_ioctl_x86_set_xsave(struct kvm_vcpu *vcpu,