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ANDROID: KVM: arm64: Avoid BUG-ing from the host abort path

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Under certain circumstances __get_fault_info() may resolve the faulting
address using the AT instruction. Given that this is being done outside
of the host lock critical section, it is racy and the resolution via AT
may fail. We currently BUG() in this situation, which is obviously less
than ideal. Moving the address resolution to the critical section may
have a performance impact, so let's keep it where it is, but bail out
and return to the host to try a second time.

Bug: 311830307
Change-Id: I26d61b04a4ccf040bd31802abb3c6b998ff4a48b
Signed-off-by: Quentin Perret <qperret@google.com>
This commit is contained in:
Quentin Perret 2023-11-27 09:31:46 +00:00 • committed by Treehugger Robot
parent c5dc4b4b3d
commit 031f804149
1 changed files with 9 additions and 1 deletions
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10
arch/arm64/kvm/hyp/nvhe/mem_protect.c
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@ -875,7 +875,14 @@ void handle_host_mem_abort(struct kvm_cpu_context *host_ctxt)
int ret = -EPERM; int ret = -EPERM;
esr = read_sysreg_el2(SYS_ESR); esr = read_sysreg_el2(SYS_ESR);
BUG_ON(!__get_fault_info(esr, &fault)); if (!__get_fault_info(esr, &fault)) {
addr = (u64)-1;
/*
* We've presumably raced with a page-table change which caused
* AT to fail, try again.
*/
goto return_to_host;
}
fault.esr_el2 = esr; fault.esr_el2 = esr;
addr = (fault.hpfar_el2 & HPFAR_MASK) << 8; addr = (fault.hpfar_el2 & HPFAR_MASK) << 8;
@ -902,6 +909,7 @@ void handle_host_mem_abort(struct kvm_cpu_context *host_ctxt)
else else
BUG_ON(ret && ret != -EAGAIN); BUG_ON(ret && ret != -EAGAIN);
return_to_host:
trace_host_mem_abort(esr, addr); trace_host_mem_abort(esr, addr);
} }