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RISC-V: KVM: Fix guest page fault within HLV* instructions

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[ Upstream commit 974555d6e417974e63444266e495a06d06c23af5 ]

When executing HLV* instructions at the HS mode, a guest page fault
may occur when a g-stage page table migration between triggering the
virtual instruction exception and executing the HLV* instruction.

This may be a corner case, and one simpler way to handle this is to
re-execute the instruction where the virtual  instruction exception
occurred, and the guest page fault will be automatically handled.

Fixes: b91f0e4cb8 ("RISC-V: KVM: Factor-out instruction emulation into separate sources")
Signed-off-by: Fangyu Yu <fangyu.yu@linux.alibaba.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20251121133543.46822-1-fangyu.yu@linux.alibaba.com
Signed-off-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Fangyu Yu
2025-11-21 21:35:43 +08:00
committed by Greg Kroah-Hartman
parent 76ae0cc396
commit e3e1c7416b
1 changed files with 22 additions and 0 deletions
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22
arch/riscv/kvm/vcpu_insn.c
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@@ -396,6 +396,22 @@ static int system_opcode_insn(struct kvm_vcpu *vcpu, struct kvm_run *run,
return (rc <= 0) ? rc : 1;
}
static bool is_load_guest_page_fault(unsigned long scause)
{
/**
* If a g-stage page fault occurs, the direct approach
* is to let the g-stage page fault handler handle it
* naturally, however, calling the g-stage page fault
* handler here seems rather strange.
* Considering this is a corner case, we can directly
* return to the guest and re-execute the same PC, this
* will trigger a g-stage page fault again and then the
* regular g-stage page fault handler will populate
* g-stage page table.
*/
return (scause == EXC_LOAD_GUEST_PAGE_FAULT);
}
/**
* kvm_riscv_vcpu_virtual_insn -- Handle virtual instruction trap
*
@@ -421,6 +437,8 @@ int kvm_riscv_vcpu_virtual_insn(struct kvm_vcpu *vcpu, struct kvm_run *run,
ct->sepc,
&utrap);
if (utrap.scause) {
if (is_load_guest_page_fault(utrap.scause))
return 1;
utrap.sepc = ct->sepc;
kvm_riscv_vcpu_trap_redirect(vcpu, &utrap);
return 1;
@@ -476,6 +494,8 @@ int kvm_riscv_vcpu_mmio_load(struct kvm_vcpu *vcpu, struct kvm_run *run,
insn = kvm_riscv_vcpu_unpriv_read(vcpu, true, ct->sepc,
&utrap);
if (utrap.scause) {
if (is_load_guest_page_fault(utrap.scause))
return 1;
/* Redirect trap if we failed to read instruction */
utrap.sepc = ct->sepc;
kvm_riscv_vcpu_trap_redirect(vcpu, &utrap);
@@ -602,6 +622,8 @@ int kvm_riscv_vcpu_mmio_store(struct kvm_vcpu *vcpu, struct kvm_run *run,
insn = kvm_riscv_vcpu_unpriv_read(vcpu, true, ct->sepc,
&utrap);
if (utrap.scause) {
if (is_load_guest_page_fault(utrap.scause))
return 1;
/* Redirect trap if we failed to read instruction */
utrap.sepc = ct->sepc;
kvm_riscv_vcpu_trap_redirect(vcpu, &utrap);