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Thu, 16 Apr 2020 16:26:05 +0100 MIME-Version: 1.0 Date: Thu, 16 Apr 2020 16:26:05 +0100 From: Marc Zyngier To: Suzuki K Poulose Subject: Re: [PATCH 8/8] arm64: cpufeature: Add an overview comment for the cpufeature framework In-Reply-To: <96dd797d-ccfe-c867-0a70-65eccacde3cd@arm.com> References: <20200414213114.2378-1-will@kernel.org> <20200414213114.2378-9-will@kernel.org> <96dd797d-ccfe-c867-0a70-65eccacde3cd@arm.com> Message-ID: <96438d59a2bc05871ef68fca475fabf5@kernel.org> X-Sender: maz@kernel.org User-Agent: Roundcube Webmail/1.3.10 X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: suzuki.poulose@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, mark.rutland@arm.com, anshuman.khandual@arm.com, catalin.marinas@arm.com, saiprakash.ranjan@codeaurora.org, dianders@chromium.org, kernel-team@android.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Cc: saiprakash.ranjan@codeaurora.org, kernel-team@android.com, anshuman.khandual@arm.com, catalin.marinas@arm.com, linux-kernel@vger.kernel.org, dianders@chromium.org, will@kernel.org, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On 2020-04-16 15:59, Suzuki K Poulose wrote: Hi Suzuki, [...] > As you mentioned in the other response we could add information about > the guest view, something like : > > - KVM exposes the sanitised value of the feature registers to the > guests and is not affected by the FTR_VISIBLE. However, > depending on the individual feature support in the hypervisor, > some of the fields may be capped/limited. Although in most cases, what KVM exposes is indeed a strict subset of the host's features, there is a few corner cases where we expose features that do not necessarily exist on the host. For example ARMv8.5-GTG and ARMv8.4-TTL get exposed by the NV patches even if they don't exist on the host, as KVM will actually emulate them. Not a big deal, but I just wanted to outline that it isn't as clear-cut as it may seem... Thanks, M. -- Jazz is not dead. It just smells funny... _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm