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Re: [Qemu-devel] [Xen-devel] [RFC] e1000: Don't save writes to ICS/ICR m
From: |
Konrad Rzeszutek Wilk |
Subject: |
Re: [Qemu-devel] [Xen-devel] [RFC] e1000: Don't save writes to ICS/ICR masked by IMS |
Date: |
Tue, 13 Sep 2016 16:59:21 -0400 |
User-agent: |
Mutt/1.6.2 (2016-07-01) |
On Thu, Sep 01, 2016 at 10:57:48AM -0700, Ed Swierk wrote:
> Windows 8, 10 and Server 2012 guests hang intermittently while booting
> on Xen 4.5.3 with 1 vCPU and 4 e1000 vNICs, shortly after the Windows
> logo appears and the little dots start spinning.
>
> Running strace on qemu shows its main thread doing the following every
> couple of milliseconds:
>
> ppoll([..., {fd=30</dev/xen/evtchn>, events=POLLIN|POLLERR|POLLHUP},
> ...], ...) = 1 ([{fd=30, revents=POLLIN}], ...)
> read(30</dev/xen/evtchn>, "^\0\0\0", 4) = 4
> write(30</dev/xen/evtchn>, "^\0\0\0", 4) = 4
> ioctl(30</dev/xen/evtchn>, IOCTL_EVTCHN_NOTIFY, 0x7f1f9449d310) = 0
> clock_gettime(CLOCK_MONOTONIC, {6937, 449468262}) = 0
> clock_gettime(CLOCK_MONOTONIC, {6937, 449582903}) = 0
> gettimeofday({1472251376, 673434}, NULL) = 0
> clock_gettime(CLOCK_MONOTONIC, {6937, 449856205}) = 0
> gettimeofday({1472251376, 673679}, NULL) = 0
>
> The event channel (identified by '^' or 94 in this example) is always
> the third of the domain's four channels.
>
> Two recent qemu patches (http://git.qemu.org/?p=qemu.git;h=9596ef7c and
> http://git.qemu.org/?p=qemu.git;h=74004e8c) seem to address similar
> issues, but don't help in this case.
>
> The proposed fix from
> https://bugzilla.redhat.com/show_bug.cgi?id=874406#c78 makes the hang
> go away. It's not clear to me why it works, or if it's just papering
> over a bug elsewhere, or if there are any possible side effects.
CC-ing Denis.
Is the fix below based on reading the spec or more of instrumenting?
Thanks.
>
> Suggested-by: Andrew Jones <address@hidden>
> Signed-off-by: Ed Swierk <address@hidden>
>
> diff --git a/hw/net/e1000.c b/hw/net/e1000.c
> index 6eac66d..c891b67 100644
> --- a/hw/net/e1000.c
> +++ b/hw/net/e1000.c
> @@ -293,6 +293,8 @@ set_interrupt_cause(E1000State *s, int index, uint32_t
> val)
> uint32_t pending_ints;
> uint32_t mit_delay;
>
> + val &= s->mac_reg[IMS];
> +
> s->mac_reg[ICR] = val;
>
> /*
> @@ -305,7 +307,7 @@ set_interrupt_cause(E1000State *s, int index, uint32_t
> val)
> */
> s->mac_reg[ICS] = val;
>
> - pending_ints = (s->mac_reg[IMS] & s->mac_reg[ICR]);
> + pending_ints = s->mac_reg[ICR];
> if (!s->mit_irq_level && pending_ints) {
> /*
> * Here we detect a potential raising edge. We postpone raising the
>
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