From: David Woodhouse <dwmw2@infradead.org>
To: Paul Durrant <paul@xen.org>, Paolo Bonzini <pbonzini@redhat.com>,
Jonathan Corbet <corbet@lwn.net>,
Sean Christopherson <seanjc@google.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Shuah Khan <shuah@kernel.org>,
kvm@vger.kernel.org, linux-doc@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org
Subject: Re: [PATCH v10 16/19] KVM: xen: split up kvm_xen_set_evtchn_fast()
Date: Thu, 14 Dec 2023 14:00:16 +0000 [thread overview]
Message-ID: <e22e354305d853d72039c7e12b166410de3f63c9.camel@infradead.org> (raw)
In-Reply-To: <20231204144334.910-17-paul@xen.org>
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On Mon, 2023-12-04 at 14:43 +0000, Paul Durrant wrote:
> From: Paul Durrant <pdurrant@amazon.com>
>
> The implementation of kvm_xen_set_evtchn_fast() is a rather lengthy piece
> of code that performs two operations: updating of the shared_info
> evtchn_pending mask, and updating of the vcpu_info evtchn_pending_sel
> mask. Introduce a separate function to perform each of those operations and
> re-work kvm_xen_set_evtchn_fast() to use them.
>
> No functional change intended.
>
> Signed-off-by: Paul Durrant <pdurrant@amazon.com>
...
> + if (IS_ENABLED(CONFIG_64BIT) && kvm->arch.xen.long_mode) {
> + struct vcpu_info *vcpu_info = gpc->khva;
> + u32 port_word_bit = port / 32;
Shouldn't that one be /64, and the compat one be /32?
> +
> + if (!kvm_gpc_check(gpc, sizeof(*vcpu_info))) {
> + if (!test_and_set_bit(port_word_bit, &vcpu->arch.xen.evtchn_pending_sel))
> + kick_vcpu = true;
> + goto out;
> + }
> +
> + if (!test_and_set_bit(port_word_bit, &vcpu_info->evtchn_pending_sel)) {
> + WRITE_ONCE(vcpu_info->evtchn_upcall_pending, 1);
> + kick_vcpu = true;
This is the one you're removing...
> - int port_word_bit;
...
> - if (IS_ENABLED(CONFIG_64BIT) && kvm->arch.xen.long_mode) {
> - struct shared_info *shinfo = gpc->khva;
> - pending_bits = (unsigned long *)&shinfo->evtchn_pending;
> - mask_bits = (unsigned long *)&shinfo->evtchn_mask;
> - port_word_bit = xe->port / 64;
> - } else {
> - struct compat_shared_info *shinfo = gpc->khva;
> - pending_bits = (unsigned long *)&shinfo->evtchn_pending;
> - mask_bits = (unsigned long *)&shinfo->evtchn_mask;
> - port_word_bit = xe->port / 32;
> - }
And why change it from an int to a u32?
On x86, arch_test_and_set_bit() takes a 'long' as its first argument,
and arch___test_and_set_bit takes an 'unsigned long'.
Then again, asm-generic/bitops/atomic.h has an arch_test_and_set_bit()
taking an 'unsigned int'. And the le version takes an 'int'.
My brain hurts. That's a complete clusterfuck and none of it seems to
have any commentary about why.
Either way, *none* of them take a u32. Why did you change to that
instead of leaving well alone? I now blame you for my headache :)
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next prev parent reply other threads:[~2023-12-14 14:00 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-04 14:43 [PATCH v10 00/19] KVM: xen: update shared_info and vcpu_info handling Paul Durrant
2023-12-04 14:43 ` [PATCH v10 01/19] KVM: pfncache: Add a map helper function Paul Durrant
2023-12-04 14:43 ` [PATCH v10 02/19] KVM: pfncache: remove unnecessary exports Paul Durrant
2023-12-04 14:43 ` [PATCH v10 03/19] KVM: xen: mark guest pages dirty with the pfncache lock held Paul Durrant
2023-12-04 14:43 ` [PATCH v10 04/19] KVM: pfncache: add a mark-dirty helper Paul Durrant
2023-12-04 14:43 ` [PATCH v10 05/19] KVM: pfncache: remove KVM_GUEST_USES_PFN usage Paul Durrant
2023-12-04 14:43 ` [PATCH v10 06/19] KVM: pfncache: stop open-coding offset_in_page() Paul Durrant
2023-12-04 14:43 ` [PATCH v10 07/19] KVM: pfncache: include page offset in uhva and use it consistently Paul Durrant
2023-12-04 14:43 ` [PATCH v10 08/19] KVM: pfncache: allow a cache to be activated with a fixed (userspace) HVA Paul Durrant
2023-12-04 14:43 ` [PATCH v10 09/19] KVM: xen: separate initialization of shared_info cache and content Paul Durrant
2023-12-14 13:41 ` David Woodhouse
2023-12-14 14:00 ` Paul Durrant
2023-12-04 14:43 ` [PATCH v10 10/19] KVM: xen: (re-)initialize shared_info if guest (32/64-bit) mode is set Paul Durrant
2023-12-14 13:44 ` David Woodhouse
2023-12-04 14:43 ` [PATCH v10 11/19] KVM: xen: allow shared_info to be mapped by fixed HVA Paul Durrant
2023-12-04 14:43 ` [PATCH v10 12/19] KVM: xen: allow vcpu_info " Paul Durrant
2023-12-04 14:43 ` [PATCH v10 13/19] KVM: selftests / xen: map shared_info using HVA rather than GFN Paul Durrant
2023-12-04 14:43 ` [PATCH v10 14/19] KVM: selftests / xen: re-map vcpu_info using HVA rather than GPA Paul Durrant
2023-12-04 14:43 ` [PATCH v10 15/19] KVM: xen: advertize the KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA capability Paul Durrant
2023-12-04 14:43 ` [PATCH v10 16/19] KVM: xen: split up kvm_xen_set_evtchn_fast() Paul Durrant
2023-12-14 14:00 ` David Woodhouse [this message]
2023-12-14 14:20 ` David Woodhouse
2023-12-04 14:43 ` [PATCH v10 17/19] KVM: xen: don't block on pfncache locks in kvm_xen_set_evtchn_fast() Paul Durrant
2023-12-14 14:03 ` David Woodhouse
2023-12-04 14:43 ` [PATCH v10 18/19] KVM: pfncache: check the need for invalidation under read lock first Paul Durrant
2023-12-14 14:08 ` David Woodhouse
2023-12-04 14:43 ` [PATCH v10 19/19] KVM: xen: allow vcpu_info content to be 'safely' copied Paul Durrant
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