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3da02409af
As reported in the community forum [0][1], QEMU processes for Linux
guests would consume more CPU on the host after an update to QEMU 9.2.
The issue was reproduced and bisecting pointed to QEMU commit
f0ccf77078 ("hpet: fix and cleanup persistence of interrupt status").
Some quick experimentation suggests that in particular the last part
is responsible for the issue:
> - the timer must be kept running even if not enabled, in
> order to set the ISR flag, so writes to HPET_TN_CFG must
> not call hpet_del_timer()
Users confirmed that setting the hpet=off machine flag works around
the issue[0]. For Windows (7 or later) guests, the flag is already
disabled, because of issues in the past [2].
Upstream suggested reverting the relevant patches for now [3], because
other issues were reported too. All except commit 5895879aca ("hpet:
remove unnecessary variable "index"") are actually dependent on each
other for cleanly reverting f0ccf77078, and while not strictly
required, that one was reverted too for completeness.
[0]: https://forum.proxmox.com/threads/163694/
[1]: https://forum.proxmox.com/threads/161849/post-756793
[2]: https://lists.proxmox.com/pipermail/pve-devel/2012-December/004958.html
[3]: https://lore.kernel.org/qemu-devel/CABgObfaKJ5NFVKmYLFmu4C0iZZLJJtcWksLCzyA0tBoz0koZ4A@mail.gmail.com/
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
41 lines
1.8 KiB
Diff
41 lines
1.8 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Fiona Ebner <f.ebner@proxmox.com>
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Date: Wed, 19 Mar 2025 17:31:12 +0100
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Subject: [PATCH] Revert "hpet: ignore high bits of comparator in 32-bit mode"
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This reverts commit 9eb7fad3546a89ee7cf0e90f5b1daccf89725cea.
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Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
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---
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hw/timer/hpet.c | 4 ----
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hw/timer/trace-events | 1 -
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2 files changed, 5 deletions(-)
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diff --git a/hw/timer/hpet.c b/hw/timer/hpet.c
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index 6f83d88516..509986c0a9 100644
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--- a/hw/timer/hpet.c
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+++ b/hw/timer/hpet.c
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@@ -585,10 +585,6 @@ static void hpet_ram_write(void *opaque, hwaddr addr,
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}
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break;
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case HPET_TN_CMP + 4: // comparator register high order
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- if (timer->config & HPET_TN_32BIT) {
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- trace_hpet_ram_write_invalid_tn_cmp();
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- break;
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- }
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trace_hpet_ram_write_tn_cmp(4);
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if (!timer_is_periodic(timer)
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|| (timer->config & HPET_TN_SETVAL)) {
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diff --git a/hw/timer/trace-events b/hw/timer/trace-events
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index 219747df2f..b86870fb22 100644
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--- a/hw/timer/trace-events
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+++ b/hw/timer/trace-events
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@@ -117,7 +117,6 @@ hpet_ram_write_timer_id(uint64_t timer_id) "hpet_ram_writel timer_id = 0x%" PRIx
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hpet_ram_write_tn_cfg(void) "hpet_ram_writel HPET_TN_CFG"
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hpet_ram_write_invalid_tn_cfg(uint8_t reg_off) "invalid HPET_TN_CFG + %" PRIu8 " write"
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hpet_ram_write_tn_cmp(uint8_t reg_off) "hpet_ram_writel HPET_TN_CMP + %" PRIu8
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-hpet_ram_write_invalid_tn_cmp(void) "invalid HPET_TN_CMP + 4 write"
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hpet_ram_write_invalid(void) "invalid hpet_ram_writel"
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hpet_ram_write_counter_write_while_enabled(void) "Writing counter while HPET enabled!"
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hpet_ram_write_counter_written(uint8_t reg_off, uint64_t value, uint64_t counter) "HPET counter + %" PRIu8 "written. crt = 0x%" PRIx64 " -> 0x%" PRIx64
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