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KVM: selftests: Drop HORRIFIC_L2_UCALL_CLOBBER_HACK

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Now that nVMX test codes preserves GPRs across nested VM-Exits
(specifically RBP, RDX, and RDI among others), drop the ucall-specific
hack to avoid clobbering these registers.

Assisted-by: Gemini:gemini-3.1-pro
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260728174232.2423257-7-yosry@kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Yosry Ahmed 2026-07-28 17:42:25 +00:00 committed by Sean Christopherson
parent 3d31fea7b6
commit 2bdef77c60
1 changed files with 2 additions and 30 deletions
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32
tools/testing/selftests/kvm/lib/x86/ucall.c
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@ -10,36 +10,8 @@
void ucall_arch_do_ucall(gva_t uc)
{
/*
* FIXME: Revert this hack (the entire commit that added it) once nVMX
* preserves L2 GPRs across a nested VM-Exit. If a ucall from L2, e.g.
* to do a GUEST_SYNC(), lands the vCPU in L1, any and all GPRs can be
* clobbered by L1. Save and restore non-volatile GPRs (clobbering RBP
* in particular is problematic) along with RDX and RDI (which are
* inputs), and clobber volatile GPRs. *sigh*
*/
#define HORRIFIC_L2_UCALL_CLOBBER_HACK \
"rcx", "rsi", "r8", "r9", "r10", "r11"
asm volatile("push %%rbp\n\t"
"push %%r15\n\t"
"push %%r14\n\t"
"push %%r13\n\t"
"push %%r12\n\t"
"push %%rbx\n\t"
"push %%rdx\n\t"
"push %%rdi\n\t"
"in %[port], %%al\n\t"
"pop %%rdi\n\t"
"pop %%rdx\n\t"
"pop %%rbx\n\t"
"pop %%r12\n\t"
"pop %%r13\n\t"
"pop %%r14\n\t"
"pop %%r15\n\t"
"pop %%rbp\n\t"
: : [port] "d" (UCALL_PIO_PORT), "D" (uc) : "rax", "memory",
HORRIFIC_L2_UCALL_CLOBBER_HACK);
asm volatile("in %[port], %%al"
: : [port] "d" (UCALL_PIO_PORT), "D" (uc) : "rax", "memory");
}
void *ucall_arch_get_ucall(struct kvm_vcpu *vcpu)