Re: [PATCH 2/2] powerpc/pseries: Dynamically increase RMA size
From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2017-02-01 05:38:04
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Sukadev Bhattiprolu [off-list ref] writes:
Paul Clarke [pc@us.ibm.com] wrote: --- From f9e9e8460206bc3fa7eaa741b9a2bde22870b9e0 Mon Sep 17 00:00:00 2001
I know it's been a while but I think it would still be good to get this in a shape that we can merge it. Comments inline ...
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From: root <redacted> Date: Thu, 4 Aug 2016 23:13:37 -0400 Subject: [PATCH 2/2] powerpc/pseries: Dynamically grow RMA size When booting a very large system with a large initrd we run out of space for the flattened device tree (FDT). To fix this we must increase the space allocated for the RMA region. The RMA size is hard-coded in the 'ibm_architecture_vec[]' and increasing the size there will apply to all systems, large and small, so we want to increase the RMA region only when necessary. When we run out of room for the FDT, set a new OF property, 'ibm,new-rma-size' to the new RMA size (512MB) and issue a client-architecture-support (CAS) call to the firmware. This will initiate a system reboot. Upon reboot we notice the new property and update the RMA size accordingly. Fix suggested by Michael Ellerman. Signed-off-by: Sukadev Bhattiprolu <redacted>diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c index f612a99..d1aaeda 100644 --- a/arch/powerpc/kernel/prom_init.c +++ b/arch/powerpc/kernel/prom_init.c@@ -87,6 +87,9 @@ int of_workarounds; #endif +#define IBM_NEW_RMA_SIZE_PROP "ibm,new-rma-size" +#define IBM_NEW_RMA_SIZE_STR "512"
The property name should really start with "linux,", as it's a Linux property, not used by firmware at all. And does it need to contain a value? Just its existence is a flag that we want to increase the RMA size. So it could just be called "linux,increase-rma-size". And we don't need a #define for the name, it's not going to change once the code is in, and a #define just obscures the actual name.
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@@ -898,6 +910,42 @@ static void fixup_nr_cores(void) ptcores[1] = (cores >> 16) & 0xff; ptcores[2] = (cores >> 8) & 0xff; ptcores[3] = cores & 0xff; + fixup_nr_cores_done = true;
That code has changed upstream, so that won't apply. But that's OK, I don't think we need to do it anyway.
+static void __init fixup_rma_size(void)
+{
+ int rc;
+ u64 size;
+ unsigned char *min_rmap;
+ phandle optnode;
+ char str[64];
+
+ optnode = call_prom("finddevice", 1, 1, ADDR("/options"));
+ if (!PHANDLE_VALID(optnode))
+ prom_panic("Cannot find /options");
+
+ /*
+ * If a prior boot specified a new RMA size, use that size in
+ * ibm_architecture_vec[]. See also increase_rma_size().
+ */
+ size = 0ULL;
+ memset(str, 0, sizeof(str));
+ rc = prom_getprop(optnode, IBM_NEW_RMA_SIZE_PROP, &str, sizeof(str));
+ if (rc <= 0)
+ return;
So this can just become something like:
rc = prom_getprop(optnode, "linux,increase-rma-size", NULL, 0)
if (rc == PROM_ERROR)
return;
val = be32_to_cpu(ibm_architecture_vec.vec2.min_rma);
ibm_architecture_vec.vec2.min_rma = cpu_to_be32(val * 2);
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@@ -946,6 +996,49 @@ static void __init prom_send_capabilities(void) } #endif /* __BIG_ENDIAN__ */ } + +static void __init increase_rma_size(void) +{ + int rc, len; + char str[64]; + phandle optnode; + + optnode = call_prom("finddevice", 1, 1, ADDR("/options")); + if (!PHANDLE_VALID(optnode)) + prom_panic("Cannot find /options"); + + /* + * If we already increased the RMA size, return. + */ + memset(str, 0, sizeof(str)); + rc = prom_getprop(optnode, IBM_NEW_RMA_SIZE_PROP, &str, sizeof(str)); + + if (!strcmp(str, IBM_NEW_RMA_SIZE_STR)) { + prom_printf("RMA size already at %.3s.\n", str); + return; + } + /* + * Otherwise, set the ibm,new-rma-size property and initiate a CAS + * reboot so the RMA size can take effect. See also init_rma_size(). + */ + len = strlen(IBM_NEW_RMA_SIZE_STR) + 1; + memcpy(str, IBM_NEW_RMA_SIZE_STR, len); + + prom_printf("Setting %s property to %s\n", IBM_NEW_RMA_SIZE_PROP, str); + rc = prom_setprop(optnode, "/options", IBM_NEW_RMA_SIZE_PROP, str, len);
We should check rc there shouldn't we? Again that code can be simpler if the property is just a flag.
+ /* Force a reboot. Will work only if ibm,fw-override-cas==false */
+ prom_send_capabilities();
+
+ prom_printf("No CAS initiated reboot? Try setting ibm,fw-override-cas to 'false' in Open Firmware\n");I'm not sure if we want to be referring to ibm,fw-override-case. I don't thing it's a documented property (not in PAPR anyway), and it's certainly IBM PFW specific even if it is. I know for a fact that on KVM you won't get rebooted here, so I think if the CAS returns we should just reboot directly. cheers