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From: | Stefan Berger |
Subject: | Re: [Qemu-devel] [PATCH v3 for-2.11 3/3] tpm_tis: Return 0 for every register in case of failure mode |
Date: | Tue, 14 Nov 2017 20:18:53 -0500 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 |
On 11/14/2017 06:47 PM, Marc-André Lureau wrote:
Hi On Tue, Nov 14, 2017 at 10:52 PM, Stefan Berger <address@hidden> wrote:Rather than returning ~0, return 0 for every register in case of failure mode. The '0' is better to indicate that there's no device there.For most registers, 0 makes more sense. However, I wonder if we shouldn't just fail to start qemu in this case... Not convincing me this is 2.11 material either. Does this fix a specific bug?
Yes, SeaBIOS detects the ~0 when it probes and thinks there's a device there. It then hangs trying to set flags and read registers to be able to use the device.
Stefan
Signed-off-by: Stefan Berger <address@hidden> --- hw/tpm/tpm_tis.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/hw/tpm/tpm_tis.c b/hw/tpm/tpm_tis.c index fec2fc6..42d647d 100644 --- a/hw/tpm/tpm_tis.c +++ b/hw/tpm/tpm_tis.c @@ -545,7 +545,7 @@ static uint64_t tpm_tis_mmio_read(void *opaque, hwaddr addr, uint8_t v; if (tpm_backend_had_startup_error(s->be_driver)) { - return val; + return 0; } switch (offset) { -- 2.5.5
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