From: Saurabh Sengar <ssengar@linux.microsoft.com>
To: kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org,
decui@microsoft.com, tglx@linutronix.de, mingo@redhat.com,
bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org,
hpa@zytor.com, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org
Cc: ssengar@microsoft.com
Subject: [PATCH] x86/hyperv: Allow 15-bit APIC IDs for VTL platforms
Date: Fri, 5 Jan 2024 02:29:26 -0800 [thread overview]
Message-ID: <1704450566-26576-1-git-send-email-ssengar@linux.microsoft.com> (raw)
The current method for signaling the compatibility of a Hyper-V host
with MSIs featuring 15-bit APIC IDs relies on a synthetic cpuid leaf.
However, for higher VTLs, this leaf is not reported, due to the absence
of an IO-APIC.
As an alternative, assume that when running at a high VTL, the host
supports 15-bit APIC IDs. This assumption is now deemed safe, as no
architectural MSIs are employed at higher VTLs.
This unblocks startup of VTL2 environments with more than 256 CPUs.
Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
---
arch/x86/hyperv/hv_vtl.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c
index 539c7b5cfa2b..1c225362f88e 100644
--- a/arch/x86/hyperv/hv_vtl.c
+++ b/arch/x86/hyperv/hv_vtl.c
@@ -16,6 +16,11 @@
extern struct boot_params boot_params;
static struct real_mode_header hv_vtl_real_mode_header;
+static bool __init hv_vtl_msi_ext_dest_id(void)
+{
+ return true;
+}
+
void __init hv_vtl_init_platform(void)
{
pr_info("Linux runs in Hyper-V Virtual Trust Level\n");
@@ -39,6 +44,8 @@ void __init hv_vtl_init_platform(void)
x86_platform.legacy.warm_reset = 0;
x86_platform.legacy.reserve_bios_regions = 0;
x86_platform.legacy.devices.pnpbios = 0;
+
+ x86_init.hyper.msi_ext_dest_id = hv_vtl_msi_ext_dest_id;
}
static inline u64 hv_vtl_system_desc_base(struct ldttss_desc *desc)
--
2.25.1
next reply other threads:[~2024-01-05 10:29 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-05 10:29 Saurabh Sengar [this message]
2024-01-10 5:10 ` [PATCH] x86/hyperv: Allow 15-bit APIC IDs for VTL platforms Michael Kelley
2024-01-14 9:24 ` Saurabh Singh Sengar
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