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Re: [PATCH] xen/acpi: Don't fail if SPCR table is absent

Hi Elliott,

On 22/10/2020 18:13, Elliott Mitchell wrote:
On Thu, Oct 22, 2020 at 09:42:17AM +0200, Jan Beulich wrote:
On 22.10.2020 00:12, Elliott Mitchell wrote:
--- a/xen/arch/arm/acpi/domain_build.c
+++ b/xen/arch/arm/acpi/domain_build.c
@@ -42,17 +42,18 @@ static int __init acpi_iomem_deny_access(struct domain *d)
      status = acpi_get_table(ACPI_SIG_SPCR, 0,
                              (struct acpi_table_header **)&spcr);
- if ( ACPI_FAILURE(status) )
+    if ( ACPI_SUCCESS(status) )
-        printk("Failed to get SPCR table\n");
-        return -EINVAL;
+        mfn = spcr->serial_port.address >> PAGE_SHIFT;
+        /* Deny MMIO access for UART */
+        rc = iomem_deny_access(d, mfn, mfn + 1);
+        if ( rc )
+            return rc;
+    }
+    else
+    {
+        printk("Failed to get SPCR table, Xen console may be unavailable\n");

Nit: While I see you've got Stefano's R-b already, I Xen we typically
omit the braces here.

Personally, I prefer that myself, but was unsure of the preference here.

I don't think we are very consistent here... I would not add them myself, but I don't particularly mind them (I know some editors will add them automatically).

I will keep them while committing. For the patch:

Acked-by: Julien Grall <jgrall@xxxxxxxxxx>

I've seen multiple projects which *really* dislike using having brackets
for some clauses, but not others (ie they want either all clauses with or
all clauses without; instead of only if required).

I sent what I thought was the more often used format.  (I also like tabs,
and dislike having so many spaces; alas my preferences are apparently

We have a few files in Xen using tabs (yes, we like mixing coding style!).


Julien Grall



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