From: "Chang S. Bae" <chang.seok.bae@intel.com>
To: pbonzini@redhat.com, seanjc@google.com
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
chao.gao@intel.com, chang.seok.bae@intel.com
Subject: [PATCH v2 03/16] KVM: x86: Implement accessors for extended GPRs
Date: Mon, 12 Jan 2026 23:53:55 +0000 [thread overview]
Message-ID: <20260112235408.168200-4-chang.seok.bae@intel.com> (raw)
In-Reply-To: <20260112235408.168200-1-chang.seok.bae@intel.com>
Add helpers to directly read and write EGPRs (R16–R31).
Unlike legacy GPRs, EGPRs are not cached in vcpu->arch.regs[]. Their
contents remain live in hardware. If preempted, the EGPR state is
preserved in the guest XSAVE buffer.
The Advanced Performance Extensions (APX) feature introduces EGPRs as an
XSAVE-managed state component. The new helpers access the registers
directly between kvm_fpu_get() and kvm_fpu_put().
Callers should ensure that EGPRs are enabled before using these helpers.
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
---
V1 -> V2: Move _kvm_read_egpr()/_kvm_write_egpr() to x86.c (Paolo)
---
arch/x86/kvm/x86.c | 70 +++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 69 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9857b4d319ed..edac2ec11e2f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1256,13 +1256,81 @@ static inline u64 kvm_guest_supported_xfd(struct kvm_vcpu *vcpu)
#endif
#ifdef CONFIG_KVM_APX
+/*
+ * Accessors for extended general-purpose registers. binutils >= 2.43 can
+ * recognize those register symbols.
+ */
+
+static void _kvm_read_egpr(int reg, unsigned long *data)
+{
+ /* mov %r16..%r31, %rax */
+ switch (reg) {
+ case __VCPU_XREG_R16: asm(".byte 0xd5, 0x48, 0x89, 0xc0" : "=a"(*data)); break;
+ case __VCPU_XREG_R17: asm(".byte 0xd5, 0x48, 0x89, 0xc8" : "=a"(*data)); break;
+ case __VCPU_XREG_R18: asm(".byte 0xd5, 0x48, 0x89, 0xd0" : "=a"(*data)); break;
+ case __VCPU_XREG_R19: asm(".byte 0xd5, 0x48, 0x89, 0xd8" : "=a"(*data)); break;
+ case __VCPU_XREG_R20: asm(".byte 0xd5, 0x48, 0x89, 0xe0" : "=a"(*data)); break;
+ case __VCPU_XREG_R21: asm(".byte 0xd5, 0x48, 0x89, 0xe8" : "=a"(*data)); break;
+ case __VCPU_XREG_R22: asm(".byte 0xd5, 0x48, 0x89, 0xf0" : "=a"(*data)); break;
+ case __VCPU_XREG_R23: asm(".byte 0xd5, 0x48, 0x89, 0xf8" : "=a"(*data)); break;
+ case __VCPU_XREG_R24: asm(".byte 0xd5, 0x4c, 0x89, 0xc0" : "=a"(*data)); break;
+ case __VCPU_XREG_R25: asm(".byte 0xd5, 0x4c, 0x89, 0xc8" : "=a"(*data)); break;
+ case __VCPU_XREG_R26: asm(".byte 0xd5, 0x4c, 0x89, 0xd0" : "=a"(*data)); break;
+ case __VCPU_XREG_R27: asm(".byte 0xd5, 0x4c, 0x89, 0xd8" : "=a"(*data)); break;
+ case __VCPU_XREG_R28: asm(".byte 0xd5, 0x4c, 0x89, 0xe0" : "=a"(*data)); break;
+ case __VCPU_XREG_R29: asm(".byte 0xd5, 0x4c, 0x89, 0xe8" : "=a"(*data)); break;
+ case __VCPU_XREG_R30: asm(".byte 0xd5, 0x4c, 0x89, 0xf0" : "=a"(*data)); break;
+ case __VCPU_XREG_R31: asm(".byte 0xd5, 0x4c, 0x89, 0xf8" : "=a"(*data)); break;
+ default: BUG();
+ }
+}
+
+static void _kvm_write_egpr(int reg, unsigned long *data)
+{
+ /* mov %rax, %r16...%r31*/
+ switch (reg) {
+ case __VCPU_XREG_R16: asm(".byte 0xd5, 0x18, 0x89, 0xc0" : : "a"(*data)); break;
+ case __VCPU_XREG_R17: asm(".byte 0xd5, 0x18, 0x89, 0xc1" : : "a"(*data)); break;
+ case __VCPU_XREG_R18: asm(".byte 0xd5, 0x18, 0x89, 0xc2" : : "a"(*data)); break;
+ case __VCPU_XREG_R19: asm(".byte 0xd5, 0x18, 0x89, 0xc3" : : "a"(*data)); break;
+ case __VCPU_XREG_R20: asm(".byte 0xd5, 0x18, 0x89, 0xc4" : : "a"(*data)); break;
+ case __VCPU_XREG_R21: asm(".byte 0xd5, 0x18, 0x89, 0xc5" : : "a"(*data)); break;
+ case __VCPU_XREG_R22: asm(".byte 0xd5, 0x18, 0x89, 0xc6" : : "a"(*data)); break;
+ case __VCPU_XREG_R23: asm(".byte 0xd5, 0x18, 0x89, 0xc7" : : "a"(*data)); break;
+ case __VCPU_XREG_R24: asm(".byte 0xd5, 0x19, 0x89, 0xc0" : : "a"(*data)); break;
+ case __VCPU_XREG_R25: asm(".byte 0xd5, 0x19, 0x89, 0xc1" : : "a"(*data)); break;
+ case __VCPU_XREG_R26: asm(".byte 0xd5, 0x19, 0x89, 0xc2" : : "a"(*data)); break;
+ case __VCPU_XREG_R27: asm(".byte 0xd5, 0x19, 0x89, 0xc3" : : "a"(*data)); break;
+ case __VCPU_XREG_R28: asm(".byte 0xd5, 0x19, 0x89, 0xc4" : : "a"(*data)); break;
+ case __VCPU_XREG_R29: asm(".byte 0xd5, 0x19, 0x89, 0xc5" : : "a"(*data)); break;
+ case __VCPU_XREG_R30: asm(".byte 0xd5, 0x19, 0x89, 0xc6" : : "a"(*data)); break;
+ case __VCPU_XREG_R31: asm(".byte 0xd5, 0x19, 0x89, 0xc7" : : "a"(*data)); break;
+ default: BUG();
+ }
+}
+
static unsigned long kvm_read_egpr(int reg)
{
- return 0;
+ unsigned long data;
+
+ if (WARN_ON_ONCE(!cpu_has_xfeatures(XFEATURE_MASK_APX, NULL)))
+ return 0;
+
+ kvm_fpu_get();
+ _kvm_read_egpr(reg, &data);
+ kvm_fpu_put();
+
+ return data;
}
static void kvm_write_egpr(int reg, unsigned long data)
{
+ if (WARN_ON_ONCE(!cpu_has_xfeatures(XFEATURE_MASK_APX, NULL)))
+ return;
+
+ kvm_fpu_get();
+ _kvm_write_egpr(reg, &data);
+ kvm_fpu_put();
}
unsigned long kvm_gpr_read_raw(struct kvm_vcpu *vcpu, int reg)
--
2.51.0
next prev parent reply other threads:[~2026-01-13 0:18 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-12 23:53 [PATCH v2 00/16] KVM: x86: Enable APX for guests Chang S. Bae
2026-01-12 23:53 ` [PATCH v2 01/16] KVM: x86: Rename register accessors to be GPR-specific Chang S. Bae
2026-03-05 1:35 ` Sean Christopherson
2026-03-07 1:32 ` Chang S. Bae
2026-03-09 23:28 ` Chang S. Bae
2026-03-10 1:23 ` Sean Christopherson
2026-03-10 22:05 ` Chang S. Bae
2026-03-10 23:12 ` Sean Christopherson
2026-01-12 23:53 ` [PATCH v2 02/16] KVM: x86: Refactor GPR accessors to differentiate register access types Chang S. Bae
2026-03-05 1:49 ` Sean Christopherson
2026-03-07 1:32 ` Chang S. Bae
2026-01-12 23:53 ` Chang S. Bae [this message]
2026-03-05 1:41 ` [PATCH v2 03/16] KVM: x86: Implement accessors for extended GPRs Sean Christopherson
2026-03-07 1:32 ` Chang S. Bae
2026-01-12 23:53 ` [PATCH v2 04/16] KVM: VMX: Introduce unified instruction info structure Chang S. Bae
2026-03-05 4:21 ` Sean Christopherson
2026-03-07 1:33 ` Chang S. Bae
2026-03-13 1:05 ` Sean Christopherson
2026-01-12 23:53 ` [PATCH v2 05/16] KVM: VMX: Refactor instruction information retrieval Chang S. Bae
2026-01-12 23:53 ` [PATCH v2 06/16] KVM: VMX: Refactor GPR index retrieval from exit qualification Chang S. Bae
2026-03-05 4:13 ` Sean Christopherson
2026-01-12 23:53 ` [PATCH v2 07/16] KVM: VMX: Support extended register index in exit handling Chang S. Bae
2026-01-12 23:54 ` [PATCH v2 08/16] KVM: nVMX: Propagate the extended instruction info field Chang S. Bae
2026-01-12 23:54 ` [PATCH v2 09/16] KVM: emulate: Support EGPR accessing and tracking Chang S. Bae
2026-03-05 4:22 ` Sean Christopherson
2026-01-12 23:54 ` [PATCH v2 10/16] KVM: emulate: Handle EGPR index and REX2-incompatible opcodes Chang S. Bae
2026-01-12 23:54 ` [PATCH v2 11/16] KVM: emulate: Support REX2-prefixed opcode decode Chang S. Bae
2026-01-12 23:54 ` [PATCH v2 12/16] KVM: emulate: Reject EVEX-prefixed instructions Chang S. Bae
2026-01-12 23:54 ` [PATCH v2 13/16] KVM: x86: Guard valid XCR0.APX settings Chang S. Bae
2026-01-12 23:54 ` [PATCH v2 14/16] KVM: x86: Expose APX foundational feature bit to guests Chang S. Bae
2026-01-19 5:55 ` Xiaoyao Li
2026-01-20 18:07 ` Edgecombe, Rick P
2026-01-20 20:50 ` Chang S. Bae
2026-01-21 19:59 ` Edgecombe, Rick P
2026-01-12 23:54 ` [PATCH v2 15/16] KVM: x86: Expose APX sub-features " Chang S. Bae
2026-01-12 23:54 ` [PATCH v2 16/16] KVM: x86: selftests: Add APX state handling and XCR0 sanity checks Chang S. Bae
2026-03-05 4:28 ` Sean Christopherson
2026-03-07 1:33 ` Chang S. Bae
2026-03-11 18:42 ` Paolo Bonzini
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