On Tue, Aug 31, 2021 at 06:50:33PM +0100, Daniel P. Berrangé wrote:
> Booting Fedora kernels with -cpu max hangs very early in boot. Disabling
> the la57 CPUID bit fixes the problem. git bisect traced the regression to
>
> commit 213ff024a2f92020290296cb9dc29c2af3d4a221 (HEAD, refs/bisect/bad)
> Author: Lara Lazier <laramglaz...@gmail.com>
> Date: Wed Jul 21 17:26:50 2021 +0200
>
> target/i386: Added consistency checks for CR4
>
> All MBZ bits in CR4 must be zero. (APM2 15.5)
> Added reserved bitmask and added checks in both
> helper_vmrun and helper_write_crN.
>
> Signed-off-by: Lara Lazier <laramglaz...@gmail.com>
> Message-Id: <20210721152651.14683-2-laramglaz...@gmail.com>
> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
>
> In this commit CR4_RESERVED_MASK is missing CR4_LA57_MASK and
> two others. Adding this lets Fedora kernels boot once again.
>
> Signed-off-by: Daniel P. Berrangé <berra...@redhat.com>
> ---
> target/i386/cpu.h | 1 +
> 1 file changed, 1 insertion(+)
>
> I don't know the implications of CR4_VMXE_MASK and CR4_SMXE_MASK
> being missing in CR4_RESERVED_MASK. It didn't cause any ill effects
> either way, but I added them on the assumption that CR4_RESERVED_MASK
> was supposed to contain all define bits.
>
> diff --git a/target/i386/cpu.h b/target/i386/cpu.h
> index 6c50d3ab4f..ce85f1a29d 100644
> --- a/target/i386/cpu.h
> +++ b/target/i386/cpu.h
> @@ -257,6 +257,7 @@ typedef enum X86Seg {
> | CR4_DE_MASK | CR4_PSE_MASK | CR4_PAE_MASK \
> | CR4_MCE_MASK | CR4_PGE_MASK | CR4_PCE_MASK \
> | CR4_OSFXSR_MASK | CR4_OSXMMEXCPT_MASK |CR4_UMIP_MASK \
> + | CR4_LA57_MASK | CR4_VMXE_MASK | CR4_SMXE_MASK \
> | CR4_FSGSBASE_MASK | CR4_PCIDE_MASK | CR4_OSXSAVE_MASK \
> | CR4_SMEP_MASK | CR4_SMAP_MASK | CR4_PKE_MASK |
> CR4_PKS_MASK))
First thing to say is I tested this locally and it fixes the
problem seen in https://bugzilla.redhat.com/show_bug.cgi?id=1999700.
I will also add this patch to Fedora soon. So:
Tested-by: Richard W.M. Jones <rjo...@redhat.com>
But my question is, does this mean that every time a new CPU feature
appears we must remember to update this code?
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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