From: Paolo Bonzini <pbonzini@redhat.com>
To: Babu Moger <babu.moger@amd.com>, richard.henderson@linaro.org
Cc: weijiang.yang@intel.com, philmd@linaro.org, dwmw@amazon.co.uk,
paul@xen.org, joao.m.martins@oracle.com, qemu-devel@nongnu.org,
mtosatti@redhat.com, kvm@vger.kernel.org, mst@redhat.com,
marcel.apfelbaum@gmail.com, yang.zhong@intel.com,
jing2.liu@intel.com, vkuznets@redhat.com, michael.roth@amd.com,
wei.huang2@amd.com, berrange@redhat.com, bdas@redhat.com
Subject: Re: [PATCH v4 4/7] target/i386: Add feature bits for CPUID_Fn80000021_EAX
Date: Fri, 5 May 2023 10:29:19 +0200 [thread overview]
Message-ID: <4ac6c060-8655-c5df-e27b-3dfb520ad388@redhat.com> (raw)
In-Reply-To: <20230504205313.225073-5-babu.moger@amd.com>
On 5/4/23 22:53, Babu Moger wrote:
> Add the following feature bits.
> no-nested-data-bp : Processor ignores nested data breakpoints.
This bit is useless, unfortunately. Another similar bit include the one
about availability of FCS/FDS in the x87 save state.
They say that something is _not_ available, so a strict interpretation
would prevent migrating from any old processor to Genoa, because in
theory you never know if guests are using nested data breakpoints.
In practice, this does not really matter because no one used
them---that's why AMD could get away with removing them---but please
tell the architects that while they're free to deprecate and remove old
features, adding CPUID is basically pointless.
Paolo
next prev parent reply other threads:[~2023-05-05 8:31 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-04 20:53 [PATCH v4 0/7] Add EPYC-Genoa model and update previous EPYC Models Babu Moger
2023-05-04 20:53 ` [PATCH v4 1/7] target/i386: allow versioned CPUs to specify new cache_info Babu Moger
2023-05-04 20:53 ` [PATCH v4 2/7] target/i386: Add new EPYC CPU versions with updated cache_info Babu Moger
2023-05-04 20:53 ` [PATCH v4 3/7] target/i386: Add a couple of feature bits in 8000_0008_EBX Babu Moger
2023-05-04 20:53 ` [PATCH v4 4/7] target/i386: Add feature bits for CPUID_Fn80000021_EAX Babu Moger
2023-05-05 8:29 ` Paolo Bonzini [this message]
2023-05-04 20:53 ` [PATCH v4 5/7] target/i386: Add missing feature bits in EPYC-Milan model Babu Moger
2023-05-04 20:53 ` [PATCH v4 6/7] target/i386: Add VNMI and automatic IBRS feature bits Babu Moger
2023-05-04 20:53 ` [PATCH v4 7/7] target/i386: Add EPYC-Genoa model to support Zen 4 processor series Babu Moger
2024-11-08 18:15 ` Maksim Davydov
2024-11-08 20:56 ` Moger, Babu
2024-11-12 10:09 ` Maksim Davydov
2024-11-12 16:23 ` Moger, Babu
2024-11-13 14:15 ` Maksim Davydov
2024-11-13 16:23 ` Moger, Babu
2024-11-14 16:59 ` Moger, Babu
2023-05-05 8:31 ` [PATCH v4 0/7] Add EPYC-Genoa model and update previous EPYC Models Paolo Bonzini
2023-05-05 17:15 ` Moger, Babu
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