From: Sean Christopherson <seanjc@google.com>
To: Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
David Woodhouse <dwmw2@infradead.org>,
Paul Durrant <paul@xen.org>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Yosry Ahmed <yosry@kernel.org>
Subject: [PATCH 03/11] KVM: x86/xen: Don't truncate RAX when handling hypercall from protected guest
Date: Thu, 9 Apr 2026 16:56:14 -0700 [thread overview]
Message-ID: <20260409235622.2052730-4-seanjc@google.com> (raw)
In-Reply-To: <20260409235622.2052730-1-seanjc@google.com>
Don't truncate RAX when handling a Xen hypercall for a guest with protected
state, as KVM's ABI is to assume the guest is in 64-bit for such cases
(the guest leaving garbage in 63:32 after a transition to 32-bit mode is
far less likely than 63:32 being necessary to complete the hypercall).
Fixes: b5aead0064f3 ("KVM: x86: Assume a 64-bit hypercall for guests with protected state")
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/xen.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 6d9be74bb673..895095dc684e 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -1678,15 +1678,14 @@ int kvm_xen_hypercall(struct kvm_vcpu *vcpu)
bool handled = false;
u8 cpl;
- input = (u64)kvm_register_read(vcpu, VCPU_REGS_RAX);
-
/* Hyper-V hypercalls get bit 31 set in EAX */
- if ((input & 0x80000000) &&
+ if ((kvm_rax_read(vcpu) & 0x80000000) &&
kvm_hv_hypercall_enabled(vcpu))
return kvm_hv_hypercall(vcpu);
longmode = is_64_bit_hypercall(vcpu);
if (!longmode) {
+ input = (u32)kvm_rax_read(vcpu);
params[0] = (u32)kvm_rbx_read(vcpu);
params[1] = (u32)kvm_rcx_read(vcpu);
params[2] = (u32)kvm_rdx_read(vcpu);
@@ -1696,6 +1695,7 @@ int kvm_xen_hypercall(struct kvm_vcpu *vcpu)
}
else {
#ifdef CONFIG_X86_64
+ input = (u64)kvm_rax_read(vcpu);
params[0] = (u64)kvm_rdi_read(vcpu);
params[1] = (u64)kvm_rsi_read(vcpu);
params[2] = (u64)kvm_rdx_read(vcpu);
--
2.53.0.1213.gd9a14994de-goog
next prev parent reply other threads:[~2026-04-09 23:56 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-09 23:56 [PATCH 00/11] KVM: x86: Clean up kvm_<reg>_{read,write}() mess Sean Christopherson
2026-04-09 23:56 ` [PATCH 01/11] KVM: SVM: Truncate INVLPGA address in compatibility mode Sean Christopherson
2026-04-09 23:56 ` [PATCH 02/11] KVM: x86/xen: Bug the VM if 32-bit KVM observes a 64-bit mode hypercall Sean Christopherson
2026-04-09 23:56 ` Sean Christopherson [this message]
2026-04-09 23:56 ` [PATCH 04/11] KVM: VMX: Read 32-bit GPR values for ENCLS instructions outside of 64-bit mode Sean Christopherson
2026-04-09 23:56 ` [PATCH 05/11] KVM: x86: Trace hypercall register *after* truncating values for 32-bit Sean Christopherson
2026-04-09 23:56 ` [PATCH 06/11] KVM: x86: Move kvm_<reg>_{read,write}() definitions to x86.h Sean Christopherson
2026-04-09 23:56 ` [PATCH 07/11] KVM: x86: Add mode-aware versions of kvm_<reg>_{read,write}() helpers Sean Christopherson
2026-04-09 23:56 ` [PATCH 08/11] KVM: x86: Drop non-raw kvm_<reg>_write() helpers Sean Christopherson
2026-04-09 23:56 ` [PATCH 09/11] KVM: nSVM: Use kvm_rax_read() now that it's mode-aware Sean Christopherson
2026-04-09 23:56 ` [PATCH 10/11] Revert "KVM: VMX: Read 32-bit GPR values for ENCLS instructions outside of 64-bit mode" Sean Christopherson
2026-04-09 23:56 ` [PATCH 11/11] KVM: x86: Harden is_64_bit_hypercall() against bugs on 32-bit kernels Sean Christopherson
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