[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[PATCH for-4.21] x86/hvm: fix reading from 0xe9 IO port if port E9 hack is active
- To: xen-devel@xxxxxxxxxxxxxxxxxxxx
- From: Roger Pau Monne <roger.pau@xxxxxxxxxx>
- Date: Thu, 2 Oct 2025 12:22:00 +0200
- Arc-authentication-results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=citrix.com; dmarc=pass action=none header.from=citrix.com; dkim=pass header.d=citrix.com; arc=none
- Arc-message-signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=5QUB8XuJaJVA7h4ehC5DNoDp0OLu6jlM/AdVcy6r/j0=; b=Zun3qwVCGSdU1lE0tqw9I0K2Cg0gZRVaWBgo+gDMlbjCIX8MhuBZ5yYJ32nekVfQ5x4hmr/xkIEmTcOYqF0+NB+L49HleKBZ+dj9zzlG4AXbvIvNbyrsEPWEtuLvwZtxSDGaUhh6NYuZlC9dMxESjw+6ZZef9SHZxTuAgNd+0oMsgjq2JAi1oDr7ruvN7MrSbgEUAI++gXoycgi5d70vr6uOQy8AaAOMtyzWNcMpdXGR5+2g6tTRLkqB2npeeVqMXgG2bn2p9kTQBhYy4FGT4V2xlAV7i/OjCQKWsyzoqUhb/JJoUjoN4xpN2fc8qRkZ8s0aLLftL4oerob+MiItYw==
- Arc-seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=HwtyMWs9h/W1KrkMJ62pVYm1sEFV5RfmUdFgeBAPACUpim8qAbQ6VieT9m2tXSlJ1/g4YTtzeLnX6PMFCJ0AzUlyGO2B8m1dF33RRyKoC6dIoYb2Hu1Ktlj8B1psudxKiEk3k43PCt6pk1+1Af/swIBFenwWQf9oxdOh9wOkSnvckByubzaXvLDRqAFPOaNy4d+0UsXRwC43cr5MLJjh27fCzo9H9azBnLhOSHg0TfPaVWcC8/M3UX8gZmLxVhTQD9TiPdLpJqfZ0DZe2K4Ki+wX6WxK6RlPmOVbNFalM/uTaR36fGnK3K1oiPdE/H7cKdjdeC3+8M/4SkAjWSyxaA==
- Authentication-results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=citrix.com;
- Cc: Roger Pau Monne <roger.pau@xxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Delivery-date: Thu, 02 Oct 2025 10:22:24 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
Reading from the E9 port if the emergency console is active should return
0xe9 according to the documentation from Bochs:
https://bochs.sourceforge.io/doc/docbook/user/bochsrc.html
See `port_e9_hack` section description.
Fix Xen so it also returns the port address. OSes can use it to detect
whether the emergency console is available or not.
Fixes: d1bd157fbc9b ("Big merge the HVM full-virtualisation abstractions.")
Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
xen/arch/x86/hvm/hvm.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 23bd7f078a1d..0c60faa39d7b 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -567,9 +567,15 @@ static int cf_check hvm_print_line(
ASSERT(bytes == 1 && port == XEN_HVM_DEBUGCONS_IOPORT);
- /* Deny any input requests. */
- if ( dir != IOREQ_WRITE )
- return X86EMUL_UNHANDLEABLE;
+ if ( dir == IOREQ_READ )
+ {
+ /*
+ * According to Bochs documentation, reading from the E9 port should
+ * return 0xE9 if the "port E9 hack" is implemented.
+ */
+ *val = XEN_HVM_DEBUGCONS_IOPORT;
+ return X86EMUL_OKAY;
+ }
if ( !is_console_printable(c) )
return X86EMUL_OKAY;
--
2.51.0
|
