70 lines
2.6 KiB
Diff
70 lines
2.6 KiB
Diff
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From 6aa786b145f484ed6e2e8a1a5089ad6e150306a8 Mon Sep 17 00:00:00 2001
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From: Sana Sharm <sansshar@redhat.com>
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Date: Fri, 3 Jan 2025 13:27:20 -0500
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Subject: [PATCH 19/19] hw/char/pl011: Use correct masks for IBRD and FBRD
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RH-Author: sansshar <None>
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RH-MergeRequest: 310: hw/char/pl011: Use correct masks for IBRD and FBRD
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RH-Jira: RHEL-67107
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Commit: [1/1] 4c7174da1dff8de3d7e2d88d84973eb69d6fc28a (sansshar/qemu-kvm-centos)
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Brew build id: 5098441
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In commit b88cfee90268cad we defined masks for the IBRD and FBRD
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integer and fractional baud rate divider registers, to prevent the
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guest from writing invalid values which could cause division-by-zero.
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Unfortunately we got the mask values the wrong way around: the FBRD
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register is six bits and the IBRD register is 16 bits, not
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vice-versa.
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You would only run into this bug if you programmed the UART to a baud
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rate of less than 9600, because for 9600 baud and above the IBRD
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value will fit into 6 bits, as per the table in
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https://developer.arm.com/documentation/ddi0183/g/programmers-model/register-descriptions/fractional-baud-rate-register--uartfbrd
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The only visible effects would be that the value read back from
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the register by the guest would be truncated, and we would
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print an incorrect baud rate in the debug logs.
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Cc: qemu-stable@nongnu.org
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Fixes: b88cfee90268 ("hw/char/pl011: Avoid division-by-zero in pl011_get_baudrate()")
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Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2610
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Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
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Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
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Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
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Reviewed-by: Gavin Shan <gshan@redhat.com>
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Message-id: 20241007144732.2491331-1-peter.maydell@linaro.org
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(cherry picked from commit cd247eae16ab1b9ce97fd34c000c1b883feeda45)
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Signed-off-by: Sana Sharma <sansshar@redhat.com>
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Changes to be committed:
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modified: hw/char/pl011.c
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---
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hw/char/pl011.c | 4 ++--
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1 file changed, 2 insertions(+), 2 deletions(-)
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diff --git a/hw/char/pl011.c b/hw/char/pl011.c
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index f8078aa216..949e9d0e0d 100644
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--- a/hw/char/pl011.c
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+++ b/hw/char/pl011.c
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@@ -88,10 +88,10 @@ DeviceState *pl011_create(hwaddr addr, qemu_irq irq, Chardev *chr)
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#define CR_LBE (1 << 7)
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/* Integer Baud Rate Divider, UARTIBRD */
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-#define IBRD_MASK 0x3f
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+#define IBRD_MASK 0xffff
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/* Fractional Baud Rate Divider, UARTFBRD */
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-#define FBRD_MASK 0xffff
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+#define FBRD_MASK 0x3f
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static const unsigned char pl011_id_arm[8] =
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{ 0x11, 0x10, 0x14, 0x00, 0x0d, 0xf0, 0x05, 0xb1 };
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--
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2.39.3
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