From: Zenghui Yu <zenghui.yu@linux.dev>
To: Alexander Graf <agraf@csgraf.de>
Cc: qemu-arm@nongnu.org, qemu-devel@nongnu.org,
peter.maydell@linaro.org, wanghaibin.wang@huawei.com
Subject: Re: [PATCH] hvf: arm: Fix encodings for ID_AA64PFR1_EL1 and debug System registers
Date: Sun, 5 May 2024 22:31:54 +0800 [thread overview]
Message-ID: <960d6344-4aa5-4644-ba97-a06d21f4ead8@linux.dev> (raw)
In-Reply-To: <f0c19830-d4e0-4585-b960-7dd3fa1a3c76@csgraf.de>
On 2024/5/5 21:18, Alexander Graf wrote:
>
> On 03.05.24 19:34, Zenghui Yu wrote:
>> We wrongly encoded ID_AA64PFR1_EL1 using {3,0,0,4,2} in
>> hvf_sreg_match[] so
>> we fail to get the expected ARMCPRegInfo from cp_regs hash table with the
>> wrong key.
>>
>> Fix it with the correct encoding {3,0,0,4,1}. With that fixed, the Linux
>> guest can properly detect FEAT_SSBS2 on my M1 HW.
>>
>> All DBG{B,W}{V,C}R_EL1 registers are also wrongly encoded with op0 == 14.
>> It happens to work because HVF_SYSREG(CRn, CRm, 14, op1, op2) equals to
>> HVF_SYSREG(CRn, CRm, 2, op1, op2), by definition. But we shouldn't
>> rely on
>> it.
>>
>> Fixes: a1477da3ddeb ("hvf: Add Apple Silicon support")
>> Signed-off-by: Zenghui Yu <zenghui.yu@linux.dev>
>
>
> Nice catch! Did you find them only because of functional issues or have
> you taken an automated pass somehow to validate the sysreg definitions
> are correct?
Neither, this was found by code inspection. I was just curious about how
VMM would interact with hypervisor to expose features to the guest. Docs
at https://developer.apple.com/documentation/hypervisor are not that
detailed (I may need to read further ;-) ).
P.S., I verified on M1 that ID_AA64PFR1_EL1 is 0x20 at
hvf_arm_get_host_cpu_features() stage and is overwritten as 0x0 later
w/o this patch, which indicates the (guest visible) feature ID registers
are "writable" to some extent.
> Reviewed-by: Alexander Graf <agraf@csgraf.de>
Thanks!
Zenghui
next prev parent reply other threads:[~2024-05-05 14:33 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-03 15:34 [PATCH] hvf: arm: Fix encodings for ID_AA64PFR1_EL1 and debug System registers Zenghui Yu
2024-05-05 13:18 ` Alexander Graf
2024-05-05 14:31 ` Zenghui Yu [this message]
2024-05-05 13:38 ` Marcin Juszkiewicz
2024-05-07 9:43 ` Peter Maydell
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